[EH] Keep filter clauses for types that have been caught.

The instruction combiner previously removed types from filter clauses in Landing Pad instructions if the type had previously been seen in a catch clause.  This is incorrect and prevents unexpected exception handlers from rethrowing the caught type.

Differential Revision: http://reviews.llvm.org/D14669

llvm-svn: 253370

1 files changed, 18 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 3ae7f08238b..dbc963a2b35 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2486,10 +2486,24 @@ Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) {
             SawCatchAll = true;
             break;
           }
-          if (AlreadyCaught.count(TypeInfo))
-            // Already caught by an earlier clause, so having it in the filter
-            // is pointless.
-            continue;
+
+          // Even if we've seen a type in a catch clause, we don't want to
+          // remove it from the filter.  An unexpected type handler may be
+          // set up for a call site which throws an exception of the same
+          // type caught.  In order for the exception thrown by the unexpected
+          // handler to propogate correctly, the filter must be correctly
+          // described for the call site.
+          //
+          // Example:
+          //
+          // void unexpected() { throw 1;}
+          // void foo() throw (int) {
+          //   std::set_unexpected(unexpected);
+          //   try {
+          //     throw 2.0;
+          //   } catch (int i) {}
+          // }
+
           // There is no point in having multiple copies of the same typeinfo in
           // a filter, so only add it if we didn't already.
           if (SeenInFilter.insert(TypeInfo).second)